This revised Phase I SBIR proposal aims at developing a topical formulation of siRNA-nanoparticle that delivers siRNA to treat skin fibrosis. Our platform has inherent antioxidant and anti-inflammatory properties, further benefitting the treatment of skin fibrosis for which there is no effective treatment. Upon completion, the platform will have broad applicability since siRNA can be designed to knock down any gene responsible for other diseases, such as psoriasis, skin disorders, and skin cancers. Our patent-pending delivery platform is a hybrid of mesoporous silica nanoparticles and co-polymer coating, which is more effective and safer than the siRNA-polyplex counterpart. Preliminary data following intradermal injection of the siRNA-NP shows promising efficacy for treating skin fibrosis in mice. A topical formulation to be developed in this Phase I proposal will significantly reduce patient burden and thus is an integral step towards clinical translation of this technology. Aim 1: We will screen appropriate vehicles for a topical siRNA-NP formulation to maximize penetration to epidermis and dermis and siRNA knockdown efficacy in a 3D human skin model. Aim 2: We will apply the optimized topical formulation to deliver siRNA against HSP47 to treat fibrosis in a 3D human skin model and benchmark against a current treatment (corticosteroid). Aim 3: Ultrasound and targeting agent (anti-EGFR antibody) will be applied on the nanoparticle to enhance penetration and cellular uptake, potentially leading to greater treatment efficacy, which will be validated in in vivo mouse study. Aim 4: Preliminary toxicity studies in cell lines, 3D human skin, and mice will be performed. The Go/No-go criteria include 1) effective topical formulation that can penetrate both epidermis and dermis layers, 2) >70% knock-down of target (HSP47) genes, 3) reduction of anti-fibrotic markers (NOX4, ?-SMA, COL I), and dermal thickness to the baseline level, 4) <15% non-specific cell death, and 5) more favorable safety and efficacy profile than the topical corticosteroid counterpart. This project is led by PDX Pharmaceuticals, LLC, a spin-off company from Biomedical Engineering Department at OHSU. The team consists of Ngamcherdtrakul, PhD, the lead developer of the siRNA- nanoparticle platform as the contact PI and Yantasee, PhD, MBA, Associate Professor at the BME of OHSU, and Oregon Nanomedicine Signature Researcher as OHSU's PI. Hardee, PhD, a former vice president of ISIS Pharmaceuticals, will serve as our formulation consultant. We utilize leased space and state-of-the-art equipment at OHSU and enjoy clinical expertise at OHSU School of Medicine. Prof. Leachman, MD, PhD, the chair of the OHSU's Dermatology Department and the pioneer of the first-in-human siRNA targeting an inherited skin disorder, will serve as our clinical consultant.